Six-dimensional quantum dynamics of dissociation of rotationally excited H2 on Cu(100)

Abstract

Six-dimensional wavepacket calculations are performed for dissociative adsorption of H₂ on Cu(100) at normal incidence. The potential-energy surface (PES) is an improved fit to points calculated using density functional theory, with the generalized gradient approximation and a slab representation for the surface. The dependence of the reaction probability on incidence energy is determined for the initial rovibrational states (v=0, j=0), (v=0, j=4, m_j=0) and (v=0, j=4, m_j=4). Owing to the use of an improved fit of the PES, the computed reaction probability for (v=0, j=0) H₂ is in better agreement with experiment than earlier 6D results for this system. At low collision energies rotational motion enhances the reaction, and taking this into account in the theoretical analysis should improve the agreement with existing molecular beam experiments. The reaction of the ‘helicopter’ (j=4, m_j=4) state is found to be more efficient than that of the ‘cartwheel’ (j=4, m_j=0) state for most of the collision energies considered.